InChI=1S/C18H16N2O8S2/c1-10-7-14(16(28-2)9-17(10)30(25,26)27)19-20-18-13-5-4-12(29(22,23)24)8-11(13)3-6-15(18)21/h3-9,21H,1-2H3,(H,22,23,24)(H,25,26,27)/b20-19+